Adding a background image/texture to stylesheet.css

[keneso]

picandnix appears to be correct. The site appears to be WordPress. If so, they should be able to advise you on their forums.

You both appear to be wrong ;)
irori's fault is s/he didn't give the site link correctly:
ishafairtrade.com.au/ <<< is wordpress
ishafairtrade.com.au/zencart <<< is zencart

I'd check for the image path, and the syntax:
.jpg); ;}

I tried with this, and it works
url("http://www.ishafairtrade.com.au/zencart/includes/templates/alysa_rounded/buttons/english/button_search_header.gif")

Put your image in
templates/alysa_rounded/images
and try again